Telemetry: extends Platform abstraction.

tools/telemetry/telemetry/possible_browser.py

 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 class PossibleBrowser(object):
   """A browser that can be controlled.
 
   Call Create() to launch the browser and begin manipulating it..
   """
 
   def __init__(self, browser_type, options):
     self.browser_type = browser_type
     self._options = options
 
   def __repr__(self):
     return 'PossibleBrowser(browser_type=%s)' % self.browser_type
 
   @property
   def options(self):
     return self._options
 
   def Create(self):
     raise NotImplementedError()
+
+  def CreatePlatformHarness(self):
+    """Returns an object responsible for setup / tear down."""
+    class EmptyPlatforHarness(object):
+      def __enter__(self):
+        return self
+
+      def __exit__(self, *args):
+        pass
+
+    return EmptyPlatforHarness()